Manometers



A. C. WILSON Feb. 14, 1967 MANOMETERS Filed Aug. 19, 1965 III it? wlwi z rill-III! United States Patent 3,303,703 MANOMETERS Alexander Connor Wilson, High Wycombe, England, as-

signor of one-half to Airflow Developments Limited,

High Wycombe, England, a British company Filed Aug. 19, 1963, Ser. No. 303,024 Claims priority, application Great Britain, Aug. 23, 1962,

2 Claims. (Cl. 73-401) This invention relates to manometers, and more particularly but not exclusively to manometers such as are used for instance for measuring a pressure drop across air filters in industrial and domestic air conditioning or warm air heating plants.

In accordance with the invention a manometer comprises a face plate, composed entirely or partly of clear synthetic plastic material and an opposed backing plate which together define a liquid reservoir, -a pressure indicating tube .and a liquid overflow chamber.

Preferably the face plate is formed with a convex rib over the front of the indicating tube, which may slope relative to the horizontal, to magnify the liquid therein and facilitate reading from a scale.

Preferably also the backing plate, which may be moulded or fabricated, has a portion projecting into the tube-forming part of the face plate to reduce the crosssectional area of the tube in relation to the cross-sectional area of the reservoir.

Further the backing plate preferably has a portion of predetermined profile projecting into the reservoir-forming part of the face plate to compensate for changes in the surface area of the liquid in the reservoir with rise and fall of the liquid when it comes into contact with the sloping lower surface of the indicating tube.

Preferably also the manometer has a scale mounted alongside the tube-forming part of the face plate and slidably adjustable thereon.

One particular and at present preferred embodiment of the invention, to be described by way of example, is illustrated in the accompanying drawings, in which:

FIGURE 1 is a front elevation;

FIGURE 2 is a front elevation with the scale and printing removed from the face plate;

FIGURE 3 is a section on line AAAA of FIGURE 2.

Referring now to the drawing the manometer comprises a horizontally elongated rectangular casing consisting of a face plate *1 made of clear synthetic plastic material and an opaque moulded backing plate 2 also of synthetic plastic material secured to the face plate 1 by adhesive.

The face plate is relatively thick compared with the backing plate 2 and has three separate intercommunicat ing cavities opening in its rear face and extending substantially longitudinally of the face plate. The upper cavity 3 is in communication with a moulded tubular inlet 4 projecting near one end of the plate and is of substantially rectangular cross-section. This cavity constitutes an overflow chamber and is in communication with a narrow slanting tube-forming cavity 5 which in turn is in communication with a rectangular cross-section cavity 6 which constitutes a liquid reservoir which is connected to a tubular vent 7 at one end of the casing.

In front of the tube-forming cavity the face plate is formed with an externally convex rib 8 to magnify to an 3,303,703 Patented Feb. 14, 1967 observer the liquid contained in the tube-forming part.

Along the front of the face plate just above this rib there is fitted a scale plate 9. This plate has a central short slot 10 through which there extends a knurled screw 11 .by which the scale plate 9 may be fixed in any required position of adjustment relative to the tube 5. This screw extends through to the rear of the face plate 1 where it receives a nut 12 located in a recess in the former.

The backing plate 2 which fits in a rebated peripheral edge part of the face plate 1 is substantially flat except for two projections 13, 14 which respectively enter the tube-forming and reservoir-forming cavities in the face plate.

The projection 13 is relatively deep and narrow and is for the purpose of reducing the cross-sectional area of the manometer tube 5 in relation to the cross-sectional area of the reservoir.

The second projection 14 is of triangular cross-section and is for the purpose of compensating for changes in the surface area of the liquid in the reservoir 6 with rise and fall of the liquid where it comes into contact with the sloping underside of the manometer indicating tube 5.

The front central part of the face plate except for the rib 8 is silk screen printed or otherwise render-ed opaque.

A manometer such as is described above has the advantage that it can be relatively inexpensively produced by comparison with currently available manometers.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A manometer comprising a face plate at least partly composed of clear synthetic plastic material, and a backing plate opposed to said face plate and defining therewith a liquid reservoir, a pressure indicating tube and a liquid overflow chamber, pressure inlet means defined by one of said plates and connected to the overflow chamber, said backing plate having a portion projecting into the pressure indicating tube to reduce the crosssectional area of said tube in relation to the cross-sectional area of the reservoir.

2. A manometer comprising a face plate at least partly composed of clear synthetic plastic material, and a backing plate opposed to said face plate and defining therewith a liquid reservoir, a pressure indicating tube with a sloping lower surface and a liquid overflow chamber, pressure inlet means defined by one of said plates and connected to the overflow chamber, said backing plate having a portion of predetermined profile projecting into the reservoir to compensate for changes in the surface area of the liquid in the reservoir with rise and fall of the liquid when it comes into contact with the sloping lower surface of the indicating tube.

References Cited by the Examiner UNITED STATES PATENTS 7/1930 Norwood. 7/1933 Dwyer 734(l1 

1. A MANOMETER COMPRISING A FACE PLATE AT LEAST PARTLY COMPOSED OF CLEAR SYNTHETIC PLASTIC MATERIAL, AND A BACKING PLATE OPPOSED TO SAID FACE PLATE AND DEFINING THEREWITH A LIQUID RESERVOIR, A PRESSURE INDICATING TUBE AND A LIQUID OVERFLOW CHAMBER, PRESSURE INLET MEANS DEFINED BY ONE OF SAID PLATES AND CONNECTED TO THE OVERFLOW CHAMBER, SAID BACKING PLATE HAVING A PORTION PROJECTING INTO THE PRESSURE INDICATING TUBE TO REDUCE THE CROSSSECTIONAL AREA OF SAID TUBE IN RELATION TO THE CROSS-SECTIONAL AREA OF THE RESERVOIR. 